The present invention relates to a water-based ink composition for ink-jet printing, an ink-jet printing method using the same and a printed matter. In particular, the present invention relates to a water-based ink composition for ink-jet printing, containing the specific dispersing resin, which is excellent in storing stability for a long period of time, discharging stability and adhesion to medium for printing, and which can be particularly suitably used for ink-jet printing methods; and relates to an ink-jet printing method using the ink composition and a printed matter produced by the printing method.
Conventionally, aqueous dye such as direct dye, acid dye or basic dye has been mainly used as a coloring agent for an ink composition for ink-jet printing. However, the aqueous dye has problems that water resistance of printed matter on paper is poor and that the aqueous dye runs with water. In addition, because the aqueous dye is poor in light resistance, the printed matter produced from the aqueous dye easily fades. Accordingly, the printed matter could not be stored for a long period of time. In order to dissolve the above problems, as disclosed in Japanese Unexamined Patent Publication No. 248210/1994 and Japanese Unexamined Patent Publication No. 194775/1997, an attempt to use pigment together with a resin has been carried out.
Recently, in accordance with a shift for a color and high-speed ink-jet printer, the so-called super penetrating ink is mainly used as ink for ink-jet printer. The super penetrating ink can penetrate in a moment after adhesion to a medium for printing. In order to impart penetrating property to ink, a penetrating agent such as a surface active agent or a penetrating solvent is added thereto. However, the penetrating agent has a problem that stable dispersion of pigment is hindered. Accordingly, it is necessitated to develop an ink composition containing pigment, of which storing stability for a long period of time can be maintained in spite of its super penetrating composition.
Furthermore, in order to produce a much close print, it is necessitated to improve impact accuracy of ink. However, it is necessitated to keep discharging stability of nozzle in order to improve impact accuracy of ink. In addition, there is a problem that it is necessitated to improve adhesion of ink to medium for printing in the existing circumstances.
An object of the present invention is to provide a water-based ink composition for ink-jet printing, which is excellent in storing stability for a long period of time in spite of its super penetrating composition, discharging stability without blinding of nozzle and adhesion to medium for printing at the same time, based on the selective use of the specific dispersing resin.
This and other objects of the present invention will become apparent from the description hereinafter.
In accordance with the present invention, there is provided
(1) a water-based ink composition for ink-jet printing, containing at least pigment, a dispersing resin, a surface active agent, an organic solvent and water, in which the pigment is dispersed with the dispersing resin, characterized in that the dispersing resin comprises a copolymer (I) prepared by polymerizing a monomer mixture (I) containing a monomer (A) represented by the formula (I): 
a monomer (B) represented by the formula (II): 
and a monomer (C) represented by the formula (III): 
and a copolymer (II) prepared by polymerizing a monomer mixture (II) containing a monomer (D) represented by the formula (IV): 
and a monomer (E) represented by the formula (V): 
(2) an ink-jet printing method characterized by discharging drops of the above water-based ink composition for ink-jet printing, fixing the drops to a medium for printing, and printing; and
(3) a printed matter produced by the above ink-jet printing method.